Electrical – Is it safe to have two circuits passing through one junction box

electricalwiring

So I found the following circuit diagram in my home. After receiving a fun little shock, I found that someone was using 14/3 cabling to carry 2 different circuits to this 1 gang box (line on left, load on right). Since the load for Circuit 2 doesn't have a matching neutral, it's connected to Circuit 1's neutral line.
Circuit

And before you ask, Circuit 1 and 2 are not MWBC circuits. Each one can be turned on/off independently. I'm presuming that this only works because the hot wires are on different phases, but this level of electrical work is a little over my head.

  1. This doesn't seem to be very safe, though it hasn't caused a fire for (presumably) a number of years.

  2. How do I go about fixing this so that it is safe?

I realize this can be and maybe should be fixed using a double pole breaker, which is certainly possible given they are neighbors in the breaker box, however I would like to keep them separate so I don't need to shut off power to half the house to work on an outlet (e.g. the circuits in the house are already on the large side of what I'd like).

Best Answer

As an answer to the last part of your updated question: If you want two separate breakers instead of a double-pole breaker, you will need to rewire from the panel to the point at which the circuits currently diverge from the 14/3 wiring so that there are truly two separate circuits without a shared neutral.

I would recommend an electrician for this type of work unless you are prepared to invest some serious time learning the NEC and acquiring the necessary permits.